title: Rhamnogalacturonan II structure shows variation in the side chains monosaccharide composition and methylation status within and across different plant species.
abstract: A paradigm regarding rhamnogalacturonans II (RGII) is their strictly conserved structure within a given plant. We developed and employed a fast structural characterization method based on chromatography and mass spectrometry, allowing analysis of RGII side chains from microgram amounts of cell wall. We found that RGII structures are much more diverse than so far described. In chain A of wild-type plants, up to 45% of the l-fucose is substituted by l-galactose, a state that is seemingly uncorrelated with RGII dimerization capacity. This led us to completely reinvestigate RGII structures of the Arabidopsis thaliana fucose-deficient mutant mur1, which provided insights into RGII chain A biosynthesis, and suggested that chain A truncation, rather than l-fucose to l-galactose substitution, is responsible for the mur1 dwarf phenotype. Mass spectrometry data for chain A coupled with NMR analysis revealed a high degree of methyl esterification of its glucuronic acid, providing a plausible explanation for the puzzling RGII antibody recognition. The β-galacturonic acid of chain A exhibits up to two methyl etherifications in an organ-specific manner. Combined with variation in the length of side chain B, this gives rise to a family of RGII structures instead of the unique structure described up to now. These findings pave the way for studies on the physiological roles of modulation of RGII composition.
authors.affiliation: Department of Chemistry, University of Natural Resources and Life Sciences, 1190, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Pabst
authors.forename: Richard M
authors.initials: RM
authors.lastname: Fischl
authors.forename: Lothar
authors.initials: L
authors.lastname: Brecker
authors.forename: Willy
authors.initials: W
authors.lastname: Morelle
authors.forename: Alexander
authors.initials: A
authors.lastname: Fauland
authors.forename: Harald
authors.initials: H
authors.lastname: Köfeler
authors.forename: Friedrich
authors.initials: F
authors.lastname: Altmann
authors.forename: Renaud
authors.initials: R
authors.lastname: Léonard
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000166:cytology / Q000235:genetics / Q000502:physiology; D002473:Cell Wall / Q000378:metabolism; D002853:Chromatography, Liquid; D005643:Fucose / Q000032:analysis / Q000378:metabolism; D005690:Galactose / Q000032:analysis / Q000737:chemistry*; D006603:Hexuronic Acids; D009005:Monosaccharides / Q000737:chemistry; D009154:Mutation; D009928:Organ Specificity; D010368:Pectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000737:chemistry* / Q000166:cytology / Q000235:genetics / Q000502:physiology; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D006603:Hexuronic Acids; D009005:Monosaccharides; C042492:rhamnogalacturonan II; D005643:Fucose; C007819:galacturonic acid; D010368:Pectins; D005690:Galactose
keywords: Arabidopsis thaliana; PGCC-ESI-MS; plant cell wall; porous graphitic carbon; rhamnogalacturonan II; structural analysis